The present invention relates to a receiver with an individual selection function for use in a mobile communication apparatus, and more particularly to the addition of a security function to prevent unauthorized use.
In a system for selecting a specified receiver by assigning a different identification number to each of a plurality of receivers and sending an identification number inherent to a receiver from a transmitter, manufacturers of such a system have been manufacturing and stock-managing individual oscillators, with a huge expense and manpower for local oscillations of the receivers, corresponding to the receiving frequencies assigned to the users (paging service companies). Recently, the receiving local oscillation frequency is generated by a synthesizer. (This system is hereafter referred to as a synthe-pager).
The synthe-pager uses an EE ROM for the data of the local oscillation frequency and an individual call number as an individual selection number ROM (hereinafter referred to as an IDROM) and selects the selection number by a ROM writer (which may comprises a pager controller for accessing the IDROM and an interface). Thus, a receiving frequency desired by a user can be selected from a common oscillator.
However, if the prior art synthe-pager is stolen, other person may use it by rewriting the frequency data by the ROM writer of the synthe-pager. Because of a risk which the user may encounter when the synthe-pager is stolen, measure to prevent it have been desired.